Method and apparatus for allocating resources in wireless access system supporting fdr transmission

ABSTRACT

The present invention relates to a wireless access system supporting a full duplex radio (FDR) transmission environment. A method for a base station for allocating resources in a wireless access systems supporting FDR according to an embodiment of the present invention comprises the steps of: selecting candidate terminals to be configured into a group from among a plurality of terminals; transmitting group configuration information to the candidate terminals; receiving, from the candidate terminals, interference information for interference between the terminals; configuring a plurality of terminals into one or more groups on the basis of the interference information; and allocating resources to the plurality of terminals on the basis of the groups.

TECHNICAL FIELD

The present invention relates to a wireless access system supporting aFull Duplex Radio (FDR) transmission environment and, more particularly,to a method for efficiently transmitting and receiving a signal when FDRis applied and an apparatus supporting the same.

BACKGROUND ART

Wireless communication systems have been widely used to provide variouskinds of communication services such as voice or data services.Generally, a wireless communication system is a multiple access systemthat can communicate with multiple users by sharing available systemresources (bandwidth, transmission (Tx) power, and the like). A varietyof multiple access systems can be used. For example, a Code DivisionMultiple Access (CDMA) system, a Frequency Division Multiple Access(FDMA) system, a Time Division Multiple Access (TDMA) system, anOrthogonal Frequency Division Multiple Access (OFDMA) system, a SingleCarrier Frequency-Division Multiple Access (SC-FDMA) system, aMulti-Carrier Frequency Division Multiple Access (MC-FDMA) system, andthe like.

DISCLOSURE Technical Problem

An object of the present invention is to provide methods for efficientlytransmitting and receiving a signal in a wireless access systemsupporting FDR transmission.

Another object of the present invention is to provide an apparatussupporting the above methods.

The technical objects that can be achieved through the present inventionare not limited to what has been particularly described hereinabove andother technical objects not described herein will be more clearlyunderstood by persons skilled in the art from the following detaileddescription.

Technical Solution

According to an aspect of the present invention devised to solve theabove problems, a method of allocating a resource by a Base Station (BS)in a wireless access system supporting Full Duplex Radio (FDR)transmission includes selecting a candidate User Equipment (UE) to beconfigured as a group among a plurality of UEs, transmitting informationabout group configuration to the candidate UE, receiving interferenceinformation about inter-device interference from the candidate UE,configuring a plurality of UEs as at least one group based on theinterference information, and allocating a resource to the UEsconfigured as the group on a group basis.

The group may be configured to include a plurality of UEs having greatinterference, and the allocating the resource may include allocating theresource such that the UEs included in the group use different resourcesand UEs included in different groups operate in a Full Duplex (FD) modeon the same resource.

The group may be configured to include UEs having values of theinterference information equal to or greater than a threshold value toconfigure a worst relation based group.

The group may be configured to include a plurality of UEs having lessinterference, and the allocating the resource may include allocating theresource such that the UEs included in the group operate in a FullDuplex (FD) mode on the same resource and UEs included in differentgroups use different resources.

The group may be configured to include UEs having values of theinterference information equal to or less than a threshold value toconfigure a best relation based group.

The interference information may include values indexed in order ofmagnitude of interference value measured by the candidate UE withrespect to a plurality of neighbor UEs.

The selecting the candidate UE may include receiving first informationas to whether the UE is able to operate in a Full Duplex (FD) mode onthe same resource, second information as to whether the UE supports anFD operation of another device although the UE is unable to operate inthe FD mode on the same resource, and third information as to whetherthe UE requests participation in grouping.

According to another aspect of the present invention, a Base Station(BS) for allocating a resource in a wireless access system supportingFull Duplex Radio (FDR) transmission includes a Radio Frequency (RF)unit and a processor, wherein the processor is configured to select acandidate User Equipment (UE) to be configured as a group among aplurality of UEs, transmit information about group configuration to thecandidate UE, receive interference information about inter-deviceinterference from the candidate UE, configure a plurality of UEs as atleast one group based on the interference information, and allocate aresource to the UEs configured as the group on a group basis.

The group may be configured to include a plurality of UEs having greatinterference, and the processor may allocate the resource such that theUEs included in the group use different resources and UEs included indifferent groups operate in a Full Duplex (1-D) mode on the sameresource.

The group may be configured to include UEs having values of theinterference information equal to or greater than a threshold value toconfigure a worst relation based group.

The group may be configured to include a plurality of UEs having lessinterference, and the processor may allocate the resource such that theUEs included in the group operate in a Full Duplex (FD) mode on the sameresource and UEs included in different groups use different resources.

The group may be configured to include UEs having values of theinterference information equal to or less than a threshold value toconfigure a best relation based group.

The interference information may include values indexed in order ofmagnitude of interference value measured by the candidate UE withrespect to a plurality of neighbor UEs.

The processor may be configured to receive first information as towhether the UE is able to operate in a Full Duplex (FD) mode on the sameresource, second information as to whether the UE supports an FDoperation of another device although the UE is unable to operate in theFD mode on the same resource, and third information as to whether the UErequests participation in grouping.

DESCRIPTION OF DRAWINGS

FIG. 1 illustrates the structure of a radio frame in 3GPP LTE.

FIG. 2 illustrates exemplary frame configurations in the structure ofthe radio frame of FIG. 1.

FIG. 3 is a diagram illustrating the structure of a downlink subframe.

FIG. 4 is a diagram illustrating the structure of an uplink subframe.

FIG. 5 illustrates the configuration of a wireless communication systemsupporting MIMO.

FIG. 6 illustrates an exemplary CRS and DRS pattern for one resourceblock.

FIG. 7 illustrates an exemplary DM RS pattern defined for the LTE-Asystem.

FIG. 8 illustrates exemplary CSI-RS patterns defined for the LTE-Asystem.

FIG. 9 is a diagram illustrating an exemplary Zero-Power (ZP) CSI-RSpattern defined in an LTE-A system.

FIG. 10 illustrates an exemplary system supporting FDR transmission.

FIG. 11 illustrates exemplary inter-device interference.

FIG. 12 illustrates an exemplary FDMA and TDMA operation when an eNBoperates in a Full Duplex (FD) mode on the same resource and UEs performmultiple access.

FIG. 13 is a flowchart illustrating an initial grouping configurationmethod according to a first embodiment of the present invention.

FIG. 14 illustrates exemplary allocation of a bit indicating whether toparticipate in grouping.

FIG. 15 illustrates exemplary arrangement of an eNB and UEs forcell-specific grouping and exemplary group configuration.

FIG. 16 illustrates arrangement based on IDI measured by UEs in order ofa high value.

FIG. 17 illustrates averages of values in columns of FIG. 16.

FIG. 18 illustrates selection of UEs for configuring a first group

FIG. 19 illustrates selection of target UEs with respect to the otherUEs except for UEs a, d, and g configured as a group.

FIG. 20 illustrates configuration of a first best relation based groupwhen IDI is arranged in order of a low value contrary to FIG. 16.

FIG. 21 illustrates selection of target UEs as in FIG. 20 except for UEsb and c to configure a second group after the UEs b and c are configuredas a group.

FIG. 22 illustrates selection of target UEs after FIG. 21.

FIG. 23 illustrates exemplary groups configured based on best relationbased grouping.

FIG. 24 is a flowchart illustrating grouping update according to asecond embodiment of the present invention.

FIG. 25 illustrates an example of determining a grouping candidate UEusing a bit for a grouping participation request and a bit indicatingwhether the UE has been included in a group.

FIG. 26 illustrates exemplary frequency allocation for IDI measurementto grouping candidate UEs.

FIG. 27 illustrates an exemplary FD mode operation performed by a UE onthe same resource.

FIG. 28 illustrates a BS and a UE that are applicable to an embodimentof the present invention.

BEST MODE

The following embodiments are proposed by combining constituentcomponents and characteristics of the present invention according to apredetermined format. The individual constituent components orcharacteristics should be considered to be optional factors on thecondition that there is no additional remark. If required, theindividual constituent components or characteristics may not be combinedwith other components or characteristics. Also, some constituentcomponents and/or characteristics may be combined to implement theembodiments of the present invention. The order of operations to bedisclosed in the embodiments of the present invention may be changed toanother. Some components or characteristics of any embodiment may alsobe included in other embodiments, or may be replaced with those of theother embodiments as necessary.

The embodiments of the present invention are disclosed on the basis of adata communication relationship between a Base Station (BS) and aterminal. In this case, the BS is used as a terminal node of a networkvia which the BS can directly communicate with the terminal. Specificoperations to be conducted by the BS in the present invention may alsobe conducted by an upper node of the BS as necessary.

In other words, it will be obvious to those skilled in the art thatvarious operations for enabling the BS to communicate with the terminalin a network composed of several network nodes including the BS will beconducted by the BS or other network nodes other than the BS. The term“BS” may be replaced with a fixed station, Node B, evolved Node B (eNBor eNode B), or an Access Point (AP) as necessary. The term “relay” maybe replaced with a Relay Node (RN) or a Relay Station (RS). The term“terminal” may also be replaced with a User Equipment (UE), a MobileStation (MS), a Mobile Subscriber Station (MSS) or a Subscriber Station(SS) as necessary.

It should be noted that specific terms disclosed in the presentinvention are proposed for the convenience of description and betterunderstanding of the present invention, and the use of these specificterms may be changed to another format within the technical scope orspirit of the present invention.

In some instances, well-known structures and devices are omitted inorder to avoid obscuring the concepts of the present invention and theimportant functions of the structures and devices are shown in blockdiagram form. The same reference numbers will be used throughout thedrawings to refer to the same or like parts.

Embodiments of the present invention are supported by standard documentsdisclosed for at least one of wireless access systems including anInstitute of Electrical and Electronics Engineers (IEEE) 802 system, a3^(rd) Generation Project Partnership (3GPP) system, a 3GPP Long TermEvolution (LTE) system, and a 3GPP2 system. In particular, the steps orparts, which are not described to clearly reveal the technical idea ofthe present invention, in the embodiments of the present invention maybe supported by the above documents. All terminology used herein may besupported by at least one of the above-mentioned documents.

The following embodiments of the present invention can be applied to avariety of wireless access technologies, for example, Code DivisionMultiple Access (CDMA), Frequency Division Multiple Access (FDMA), TimeDivision Multiple Access (TDMA), Orthogonal Frequency Division MultipleAccess (OFDMA), Single Carrier Frequency Division Multiple Access(SC-FDMA), and the like. CDMA may be embodied with wireless (or radio)technology such as Universal Terrestrial Radio Access (UTRA) orCDMA2000. TDMA may be embodied with wireless (or radio) technology suchas Global System for Mobile communications (GSM)/General Packet RadioService (GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA maybe embodied with wireless (or radio) technology such as Institute ofElectrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16(WiMAX), IEEE 802-20, and Evolved UTRA (E-UTRA). UTRA is a part ofUniversal Mobile Telecommunications System (UMTS). 3rd GenerationPartnership Project Long Term Evolution (3GPP LTE) is a part of EvolvedUMTS (E-UMTS), which uses E-UTRA. 3GPP LTE employs OFDMA in downlink andemploys SC-FDMA in uplink. LTE-Advanced (LTE-A) is an evolution of 3GPPLTE. WiMAX can be explained by an IEEE 802.16e (WirelessMAN-OFDMAReference System) and an advanced IEEE 802.16m (WirelessMAN-OFDMAAdvanced System). For clarity, the following description focuses on the3GPP LTE and LTE-A systems. However, the technical features of thepresent invention are not limited thereto.

FIG. 1 illustrates the structure of a radio frame in 3GPP LTE. Framestructure type 2 is illustrated in FIG. 1. Frame structure type 2 isapplicable to a Time Division Duplex (TDD) system. One radio frame has alength of T_(f)=307200·T_(s)=10 ms and includes two half frames eachhaving a length of 153600·T_(s)=5 ms. Each half frame includes 5subframes each having a length of 30720·T_(s)=1 ms. An i-th subframeincludes two slots 2i and 2i+1 each having a length ofT_(slot)=15360·T_(s)=0.5 ms. Ts is a sampling time given as Ts=1/(15kHz×2048)=3.2552×10-8 (about 33 ns).

Frame structure type 2 includes a special subframe having three fields:a Downlink Pilot Time Slot (DwPTS), a Guard Period (GP), and an UplinkPilot Time Slot (UpPTS). The DwPTS is used for initial cell search,synchronization, or channel estimation at a UE. The UpPTS is used forchannel estimation and uplink transmission synchronization with a UE atan eNB. The GP is used to cancel interference between an uplink and adownlink, caused by multi-path delay of a downlink signal. The DwPTS,the GP, and the UpPTS are included in the special subframe of Table 1.

FIG. 2 illustrates exemplary frame configurations in the structure ofthe radio frame of FIG. 1.

In FIG. 2, D denotes a subframe for downlink transmission, U denotes asubframe for uplink transmission, and S denotes a special subframe for aguard time.

All UEs in each cell commonly have one frame configuration in theconfigurations of FIG. 2. That is, a frame configuration varies with acell, the frame configuration may be called a cell-specificconfiguration.

FIG. 3 is a diagram illustrating the structure of a downlink subframe.Up to three OFDM symbols at the start of a first slot of one subframecorresponds to a control region to which a control channel is allocated.The remaining OFDM symbols correspond to a data region to which aPhysical Downlink Shared Channel (PDSCH) is allocated. A basictransmission unit is one subframe. That is, a PDCCH and a PDSCH areallocated across two slots. Examples of the downlink control channelsused in the 3GPP LTE system include, for example, a Physical ControlFormat Indicator Channel (PCFICH), a Physical Downlink Control Channel(PDCCH), a Physical Hybrid automatic repeat request Indicator Channel(PHICH), etc. The PCFICH is located in the first OFDM symbol of asubframe, carrying information about the number of OFDM symbols used forcontrol channels in the subframe. The PHICH includes a HARQACKnowledgment/Negative ACKnowledgment (ACK/NACK) signal as a responseto an uplink transmission. The control information transmitted on thePDCCH is referred to as Downlink Control Information (DCI). The DCIincludes uplink or downlink scheduling information or an uplink transmitpower control command for a certain UE group. The PDCCH may includeinformation about resource allocation and transmission format of aDownlink Shared Channel (DL-SCH), resource allocation information of anUplink Shared Channel (UL-SCH), paging information of a Paging Channel(PCH), system information on the DL-SCH, information about resourceallocation of an higher layer control message such as a Random AccessResponse (RAR) transmitted on the PDSCH, a set of transmit power controlcommands for individual UEs in a certain UE group, transmit powercontrol information, information about activation of Voice over IP(VoIP), etc. A plurality of PDCCHs may be transmitted in the controlregion. A UE may monitor the plurality of PDCCHs. The PDCCHs aretransmitted on an aggregation of one or several contiguous ControlChannel Elements (CCEs). A CCE is a logical allocation unit used toprovide the PDCCHs at a coding rate based on the state of a radiochannel. The CCE includes a set of REs. A format and the number ofavailable bits for the PDCCH are determined based on the correlationbetween the number of CCEs and the coding rate provided by the CCEs. TheBS determines a PDCCH format according to DCI to be transmitted to theUE, and attaches a Cyclic Redundancy Check (CRC) to control information.The CRC is masked by a Radio Network Temporary Identifier (RNTI)according to the owner or usage of the PDCCH. If the PDCCH is for aspecific UE, the CRC may be masked by a cell-RNTI (C-RNTI) of the UE. Ifthe PDCCH is for a paging message, the CRC may be masked by a pagingindicator identifier (P-RNTI). If the PDCCH is for system information(more specifically, a System Information Block (SIB)), the CRC may bemasked by a system information identifier and a System Information RNTI(SI-RNTI). To indicate a random access response to a random accesspreamble received from the UE, the CRC may be masked by a randomaccess-RNTI (RA-RNTI).

FIG. 4 is a diagram illustrating the structure of an uplink subframe.The uplink subframe may be divided into a control region and a dataregion in the frequency domain. A Physical Uplink Control Channel(PUCCH) including uplink control information is allocated to the controlregion. A Physical uplink Shared Channel (PUSCH) including user data isallocated to the data region. In order to maintain single carrierproperty, one UE does not simultaneously transmit the PUCCH and thePUSCH. A PUCCH for one UE is allocated to an RB pair in a subframe. TheRBs of the RB pair occupy different subcarriers in two slots. Thus, theRB pair allocated to the PUCCH is “frequency-hopped” over a slotboundary.

Modeling of Multiple Input Multiple Output (MIMO) System

The MIMO system increases data transmission/reception efficiency using aplurality of Tx antennas and a plurality of Rx antennas. MIMO is anapplication of putting data segments received from a plurality ofantennas into a whole message, without depending on a single antennapath to receive the whole message.

MIMO schemes are classified into spatial diversity and spatialmultiplexing. Spatial diversity increases transmission reliability or acell radius using diversity gain and thus is suitable for datatransmission for a fast moving UE. In spatial multiplexing, multiple Txantennas simultaneously transmit different data and thus high-speed datacan be transmitted without increasing a system bandwidth.

FIG. 5 illustrates the configuration of a wireless communication systemsupporting multiple antennas. Referring to FIG. 5(a), when the number ofTransmission (Tx) antennas and the number of Reception (Rx) antennas areincreased to NT and NR, respectively at both a transmitter and areceiver, a theoretical channel transmission capacity increases inproportion to the number of antennas, compared to use of a plurality ofantennas at only one of the transmitter and the receiver. Therefore,transmission rate and frequency efficiency are remarkably increased.Along with the increase of channel transmission capacity, thetransmission rate may be increased in theory to the product of a maximumtransmission rate Ro that may be achieved in case of a single antennaand a rate increase rate Ri.

R _(i)=min(N _(T) ,N _(R))  [Equation 1]

For instance, a MIMO communication system with four Tx antennas and fourRx antennas may achieve a four-fold increase in transmission ratetheoretically, relative to a single-antenna wireless communicationsystem. Since the theoretical capacity increase of the MIMO wirelesscommunication system was proved in the mid 1990's, many techniques havebeen actively studied to increase data rate in real implementation. Someof the techniques have already been reflected in various wirelesscommunication standards including standards for 3G mobilecommunications, future-generation Wireless Local Area Network (WLAN),etc.

Concerning the research trend of MIMO up to now, active studies areunderway in many respects of MIMO, inclusive of studies of informationtheory related to calculation of multi-antenna communication capacity indiverse channel environments and multiple access environments, studiesof measuring MIMO radio channels and MIMO modeling, studies oftime-space signal processing techniques to increase transmissionreliability and transmission rate, etc.

Communication in a MIMO system with NT Tx antennas and NR Rx antennaswill be described in detail through mathematical modeling.

Regarding a transmission signal, up to NT pieces of information can betransmitted through the NT Tx antennas, as expressed as the followingvector.

s=└s ₁ ,s ₂ , . . . ,s _(N) _(T) ┘^(T)  [Equation 2]

A different transmission power may be applied to each piece oftransmission information, s₁, s₂, . . . , s_(N) _(T) . Let the transmitpower levels of the transmission information be denoted by P₁, P₂, . . ., P_(N) _(T) , respectively. Then the transmission power-controlledtransmission information vector may be given as

ŝ=[ŝ ₁ ,ŝ ₂ , . . . , ŝ _(N) _(T) ]^(T) =[P ₁ s ₁ ,P ₂ s ₂ , . . . ,P_(N) _(T) s _(N) _(T) ]^(T)  [Equation 3]

The transmission power-controlled transmission information vector ŝ maybe expressed as follows, using a diagonal matrix P of transmissionpower.

$\begin{matrix}{\hat{s} = {{\begin{bmatrix}P_{1} & \; & \; & 0 \\\; & P_{2} & \; & \; \\\; & \; & \ddots & \; \\0 & \; & \; & P_{N_{T}}\end{bmatrix}\begin{bmatrix}s_{1} \\s_{2} \\\vdots \\s_{N_{T}}\end{bmatrix}} = {Ps}}} & \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack\end{matrix}$

N_(T) transmission signals x₁, x₂, . . . , x_(N) _(T) may be generatedby multiplying the transmission power-controlled information vector ŝ bya weight matrix W. The weight matrix W functions to appropriatelydistribute the transmission information to the Tx antennas according totransmission channel states, etc. These N_(T) transmission signals x₁,x₂, . . . , x_(N) _(T) are represented as a vector x, which may bedetermined as

$\begin{matrix}{x = {\left\lbrack \begin{matrix}x_{1} \\x_{2} \\\vdots \\x_{i} \\\vdots \\x_{N_{T}}\end{matrix} \right\rbrack = {{\begin{bmatrix}w_{11} & w_{12} & \ldots & w_{1N_{T}} \\w_{21} & w_{22} & \ldots & w_{2N_{T}} \\\vdots & \; & \ddots & \; \\w_{i\; 1} & w_{i\; 2} & \ldots & w_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\w_{N_{T}1} & w_{N_{T}2} & \ldots & w_{N_{T}N_{T}}\end{bmatrix}\begin{bmatrix}{\hat{s}}_{1} \\{\hat{s}}_{2} \\\vdots \\{\hat{s}}_{j} \\\vdots \\{\hat{s}}_{N_{T}}\end{bmatrix}} = {{W\hat{s}} = {WPs}}}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

Here, w_(ij) denotes a weight between a jth piece of information and anith Tx antenna and W is a precoding matrix.

The transmitted signal x may be differently processed using according totwo schemes (for example, spatial diversity and spatial multiplexing).In spatial multiplexing, different signals are multiplexed andtransmitted to a receiver such that elements of information vector(s)have different values. In spatial diversity, the same signal isrepeatedly transmitted through a plurality of channel paths such thatelements of information vector(s) have the same value. Spatialmultiplexing and spatial diversity may be used in combination. Forexample, the same signal may be transmitted through three Tx antennas inspatial diversity, while the remaining signals may be transmitted to thereceiver in spatial multiplexing.

Given NR Rx antennas, signals received at the Rx antennas, y₁, y₂, . . .y_(N) _(R) may be represented as the following vector.

y=[y ₁ ,y ₂ , . . . ,y _(N) _(R) ]^(T)  [Equation 6]

When channels are modeled in the MIMO wireless communication system,they may be distinguished according to the indexes of Tx and Rxantennas. A channel between a jth Tx antenna and an ith Rx antenna isdenoted by hij. Notably, the index of an Rx antenna precedes the indexof a Tx antenna in hij.

FIG. 5(b) illustrates channels from NT Tx antennas to an ith Rx antenna.The channels may be collectively represented as a vector or a matrix.Referring to FIG. 5(b), the channels from the NT Tx antennas to the ithRx antenna may be expressed as

h _(i) ^(T) =[h _(i1) ,h _(i2) , . . . ,h _(iN) _(T) ]  [Equation 7]

Hence, all channels from the N_(T) Tx antennas to the N_(R) Rx antennasmay be expressed as the following matrix.

$\begin{matrix}{H = {\begin{bmatrix}h_{1}^{T} \\h_{2}^{T} \\\vdots \\h_{i}^{T} \\\vdots \\h_{N_{R}}^{T}\end{bmatrix} = \begin{bmatrix}h_{11} & h_{12} & \ldots & h_{1N_{T}} \\h_{21} & h_{22} & \ldots & h_{2N_{T}} \\\vdots & \; & \ddots & \; \\h_{i\; 1} & h_{i\; 2} & \ldots & h_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\h_{N_{R}1} & h_{N_{R}2} & \ldots & h_{N_{R}N_{T}}\end{bmatrix}}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack\end{matrix}$

Actual channels experience the above channel matrix H and then are addedwith Additive White Gaussian Noise (AWGN). The AWGN added to the NR Rxantennas is given as the following vector.

n=[n ₁ ,n ₂ , . . . ,n _(N) _(R) ]^(T)  [Equation 9]

From the above mathematical modeling, the received signal vector isgiven as

$\begin{matrix}{y = {\begin{bmatrix}y_{1} \\y_{2} \\\vdots \\y_{i} \\\vdots \\y_{N_{R}}\end{bmatrix} = {{{\begin{bmatrix}h_{11} & h_{12} & \ldots & h_{1N_{T}} \\h_{21} & h_{22} & \ldots & h_{2N_{T}} \\\vdots & \; & \ddots & \; \\h_{i\; 1} & h_{i\; 2} & \ldots & h_{{iN}_{T}} \\\vdots & \; & \ddots & \; \\h_{N_{R}1} & h_{N_{R}2} & \ldots & h_{N_{R}N_{T}}\end{bmatrix}\begin{bmatrix}x_{1} \\x_{2} \\\vdots \\x_{j} \\\vdots \\x_{N_{T}}\end{bmatrix}} + \begin{bmatrix}n_{1} \\n_{2} \\\vdots \\n_{i} \\\vdots \\n_{N_{R}}\end{bmatrix}} = {{Hx} + n}}}} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack\end{matrix}$

The numbers of rows and columns in the channel matrix H representingchannel states are determined according to the numbers of Rx and Txantennas. Specifically, the number of rows in the channel matrix H isequal to the number of Rx antennas, NR and the number of columns in thechannel matrix H is equal to the number of Tx antennas, NT. Hence, thechannel matrix H is of size NR×NT.

The rank of a matrix is defined as the smaller between the number ofindependent rows and the number of independent columns in the matrix.Accordingly, the rank of the matrix is not larger than the number ofrows or columns of the matrix. The rank of the channel matrix H, rank(H)satisfies the following constraint.

rank(H)≦min(N _(T) ,N _(R))  [Equation 11]

In MIMO transmission, the term “rank” denotes the number of paths forindependently transmitting signals, and the term “number of layers”denotes the number of signal streams transmitted through respectivepaths. In general, since a transmitter transmits as many layers as thenumber of ranks used for signal transmission, the rank has the samemeaning as the number of layers unless otherwise noted.

Reference Signals (RSs)

In a wireless communication system, a packet is transmitted on a radiochannel. In view of the nature of the radio channel, the packet may bedistorted during the transmission. To receive the signal successfully, areceiver should compensate for the distortion of the received signalusing channel information. Generally, to enable the receiver to acquirethe channel information, a transmitter transmits a signal known to boththe transmitter and the receiver and the receiver acquires knowledge ofchannel information based on the distortion of the signal received onthe radio channel. This signal is called a pilot signal or an RS.

In case of data transmission and reception through multiple antennas,knowledge of channel states between Tx antennas and Rx antennas isrequired for successful signal reception. Accordingly, an RS shouldexist for each Tx antenna.

In a mobile communication system, RSs are largely categorized into twotypes according to the purposes that they serve, RSs used foracquisition of channel information and RSs used for data demodulation.The former-type RSs should be transmitted in a wideband to enable UEs toacquire downlink channel information. Even UEs that do not receivedownlink data in a specific subframe should be able to receive such RSsand measure them. When an eNB transmits downlink data, it transmits thelatter-type RSs in resources allocated to the downlink data. A UE canperform channel estimation by receiving the RSs and thus demodulate databased on the channel estimation. These RSs should be transmitted in adata transmission region.

In the legacy 3GPP LTE system (e.g. one conforming to 3GPP LTERelease-8), two types of downlink RSs are defined for unicast service,Common RS (CRS) and Dedicated RS (DRS). CRS is used for CSI acquisitionand measurement, for example, for handover. The CRS is also called acell-specific RS. DRS is used for data demodulation, called aUE-specific RS. The legacy 3GPP LTE system uses the DRS only for datademodulation and the CRS for the two purposes of channel informationacquisition and data demodulation.

CRSs, which are cell-specific, are transmitted across a wideband inevery subframe. According to the number of Tx antennas at an eNB, theeNB may transmit CRSs for up to four antenna ports. For instance, an eNBwith two Tx antennas transmits CRSs for antenna port 0 and antennaport 1. If the eNB has four Tx antennas, it transmits CRSs forrespective four Tx antenna ports, antenna port 0 to antenna port 3.

FIG. 6 illustrates a CRS and DRS pattern for an RB (including 14 OFDMsymbols in time by 12 subcarriers in frequency in case of a normal CP)in a system where an eNB has four Tx antennas. In FIG. 6, REs labeledwith ‘R0’, ‘R1’, ‘R2’ and ‘R3’ represent the positions of CRSs forantenna port 0 to antenna port 4, respectively. REs labeled with ‘D’represent the positions of DRSs defined in the LTE system.

The LTE-A system, an evolution of the LTE system, can support up toeight Tx antennas. Therefore, it should also support RSs for up to eightTx antennas. Because downlink RSs are defined only for up to four Txantennas in the LTE system, RSs should be additionally defined for fiveto eight Tx antenna ports, when an eNB has five to eight downlink Txantennas in the LTE-A system. Both RSs for channel measurement and RSsfor data demodulation should be considered for up to eight Tx antennaports.

One of significant considerations for design of the LTE-A system isbackward compatibility. Backward compatibility is a feature thatguarantees a legacy LTE terminal to operate normally even in the LTE-Asystem. If RSs for up to eight Tx antenna ports are added to atime-frequency area in which CRSs defined by the LTE standard aretransmitted across a total frequency band in every subframe, RS overheadbecomes huge. Therefore, new RSs should be designed for up to eightantenna ports in such a manner that RS overhead is reduced.

Largely, new two types of RSs are introduced to the LTE-A system. Onetype is CSI-RS serving the purpose of channel measurement for selectionof a transmission rank, a Modulation and Coding Scheme (MCS), aPrecoding Matrix Index (PMI), etc. The other type is Demodulation RS (DMRS) for demodulation of data transmitted through up to eight Txantennas.

Compared to the CRS used for both purposes of measurement such aschannel measurement and measurement for handover and data demodulationin the legacy LTE system, the CSI-RS is designed mainly for channelestimation, although it may also be used for measurement for handover.Since CSI-RSs are transmitted only for the purpose of acquisition ofchannel information, they may not be transmitted in every subframe,unlike CRSs in the legacy LTE system. Accordingly, CSI-RSs may beconfigured so as to be transmitted intermittently (e.g. periodically)along the time axis, for reduction of CSI-RS overhead.

When data is transmitted in a downlink subframe, DM RSs are alsotransmitted dedicatedly to a UE for which the data transmission isscheduled. Thus, DM RSs dedicated to a particular UE may be designedsuch that they are transmitted only in a resource area scheduled for theparticular UE, that is, only in a time-frequency area carrying data forthe particular UE.

FIG. 7 illustrates an exemplary DM RS pattern defined for the LTE-Asystem. In FIG. 7, the positions of REs carrying DM RSs in an RBcarrying downlink data (an RB having 14 OFDM symbols in time by 12subcarriers in frequency in case of a normal CP) are marked. DM RSs maybe transmitted for additionally defined four antenna ports, antenna port7 to antenna port 10 in the LTE-A system. DM RSs for different antennaports may be identified by their different frequency resources(subcarriers) and/or different time resources (OFDM symbols). This meansthat the DM RSs may be multiplexed in Frequency Division Multiplexing(FDM) and/or Time Division Multiplexing (TDM). If DM RSs for differentantenna ports are positioned in the same time-frequency resources, theymay be identified by their different orthogonal codes. That is, these DMRSs may be multiplexed in Code Division Multiplexing (CDM). In theillustrated case of FIG. 7, DM RSs for antenna port 7 and antenna port 8may be located on REs of DM RS CDM group 1 through multiplexing based onorthogonal codes. Similarly, DM RSs for antenna port 9 and antenna port10 may be located on REs of DM RS CDM group 2 through multiplexing basedon orthogonal codes.

FIG. 8 illustrates exemplary CSI-RS patterns defined for the LTE-Asystem. In FIG. 8, the positions of REs carrying CSI-RSs in an RBcarrying downlink data (an RB having 14 OFDM symbols in time by 12subcarriers in frequency in case of a normal CP) are marked. One of theCSI-RS patterns illustrated in FIGS. 8(a) to 8(e) is available for anydownlink subframe. CSI-RSs may be transmitted for eight antenna portssupported by the LTE-A system, antenna port 15 to antenna port 22.CSI-RSs for different antenna ports may be identified by their differentfrequency resources (subcarriers) and/or different time resources (OFDMsymbols). This means that the CSI-RSs may be multiplexed in FDM and/orTDM. CSI-RSs positioned in the same time-frequency resources fordifferent antenna ports may be identified by their different orthogonalcodes. That is, these DM RSs may be multiplexed in CDM. In theillustrated case of FIG. 8(a), CSI-RSs for antenna port 15 and antennaport 16 may be located on REs of CSI-RS CDM group 1 through multiplexingbased on orthogonal codes. CSI-RSs for antenna port 17 and antenna port18 may be located on REs of CSI-RS CDM group 2 through multiplexingbased on orthogonal codes. CSI-RSs for antenna port 19 and antenna port20 may be located on REs of CSI-RS CDM group 3 through multiplexingbased on orthogonal codes. CSI-RSs for antenna port 21 and antenna port22 may be located on REs of CSI-RS CDM group 4 through multiplexingbased on orthogonal codes. The same principle described with referenceto FIG. 8(a) is applicable to the CSI-RS patterns illustrated in FIGS.8(b) to 8(e).

FIG. 9 is a diagram illustrating an exemplary Zero-Power (ZP) CSI-RSpattern defined in an LTE-A system. A ZP CSI-RS is largely used for twopurposes. First, the ZP CSI-RS is used to improve CSI-RS performance.That is, one network may mute a CSI-RS RE of another network in order toimprove CSI-RS measurement performance of the other network and inform aUE thereof of the muted RE by setting the muted RE to a ZP CSI-RS sothat the UE may correctly perform rate matching. Second, the ZP CSI-RSis used for interference measurement for CoMP CQI calculation. That is,some networks may mute a ZP CRS-RS RE and a UE may calculate a CoMP CQIby measuring interference from the ZP CSI-RS.

The RS patterns of FIGS. 6 to 9 are purely exemplary and an RS patternapplied to various embodiments of the present invention is not limitedto such specific RS patterns. In other words, even when an RS patterndifferent from the RS patterns of FIGS. 6 to 9 is defined and used,various embodiments of the present invention may be identically applied.

Full Duplex Radio (FDR) Transmission

A system supporting FDR refers to a system capable of simultaneouslysupporting transmission and reception using the same resource in atransmission device. For example, an eNB or a UE supporting FDRtransmission may perform transmission without performing uplink/downlinkduplexing in frequency/time, etc.

FIG. 10 illustrates an exemplary system supporting FDR transmission.

Referring to FIG. 10, two types of interference exist in the FDR system.

The first is intra-device interference indicating that a signaltransmitted over a transmission antenna of an FDR device acts asinterference by being received by a reception antenna of the FDR device.Generally, a self-interference signal is received with higher power thana desired signal. Therefore, it is important to completely cancelintra-device interference through an interference cancellationoperation.

The second is inter-device interference in which an uplink signaltransmitted by an eNB or a UE acts as interference by being received byan adjacent eNB or UE.

In a legacy communication system, since half duplex (e.g., FDD or TDD)in which uplink/downlink transmission is separately performed infrequency or time is implemented, no interference occurs between uplinkand downlink. However, an FDR transmission environment in which uplinkand downlink share the same frequency/time resource may causeinterference between an FDR device and an adjacent device.

Although interference between adjacent cells in the legacy communicationsystem still occurs even in the FDR system, this will not be covered inthe present invention.

FIG. 11 illustrates exemplary inter-device interference.

As described above, Inter-Device Interference (IDI) occurs only in FDRtransmission using the same resource in a cell. Referring to FIG. 11, anuplink signal transmitted by UE 1 to an eNB may act as interference withrespect to UE 2. While two UEs are simply illustrated in FIG. 11 forconvenience of description of IDI, features of the present invention arenot limited to the number of UEs.

FIG. 12 illustrates an exemplary FDMA and TDMA operation when an eNBoperates in a Full Duplex (FD) mode on the same resource and UEs performmultiple access.

In an FDR system, there may be FD that does not use the same resource aswell as FD that uses the same resource.

Referring to FIG. 12, a total of two groups performing an FD operationon the same resource may be configured. One is a group including UE1 andUE2 and the other is a group including UE3 and UE4. Since IDI occurs ineach group using the same resource, it is desirable that UEs generatingless IDI be configured as a group.

For example, if interference caused by UE2 has a greater effect on UE4than on UE1, UE1 and UE2 may be configured as one group as illustratedin FIG. 2.

Meanwhile, if excessive IDI caused by UE2 affects UE1, UE2 and UE1 maybe configured not to use the same resource. For example, in FDMA, atotal of three frequency bands may be allocated so that a group of UE3and UE4 uses the same frequency region and UE1 and UE2 use differentfrequency regions. In this case, while resource consumption increases,more efficient transmission can be performed in terms of overallperformance, for example, throughput.

Although technology for grouping UEs among a plurality of UEs for an FDoperation on the same resource is needed, there has been no methodcapable of implementing this technology.

Similar technology for measuring inter-cell interference or selecting acell according to interference has been used in the field of CoordinatedMulti-Point (CoMP). In CoMP, a UE located at a boundary between cellsdetermines an eNB by measuring interference of neighbor cells. However,interference in this case means signals of multiple cells affecting oneUE and, since the UE does not share resources between UEs, the UE doesnot consider IDI of neighbor UEs.

As another technology, a multi-user MIMO or virtual MIMO methodconfigures a virtual MIMO system with an eNB having a plurality ofantennas by grouping UEs each having one antenna. In multi-user MIMO,UEs receive downlink transmission information of other UEs whiledownlink transmission is performed so that IDI occurs. In this case, aneNB performs scheduling on UEs, channels between the UEs and the eNBhaving an orthogonal relationship, in order to avoid IDI. On the otherhand, the present invention relates to IDI in FD in which downlinktransmission and uplink transmission as well as downlink transmissionare simultaneously performed.

The present invention describes a method of determining a group of UEsfor IDI avoidance or mitigation and measuring and reporting IDI usingthe group of the UEs in a system using FD communication on the sameresource.

In the present invention, a device (e.g., an eNB or a UE) supporting anFD mode on the same resource is referred to as an FDR device, eNB, orUE.

The FDR device may include a self-interference canceller and the FDRdevice including the self-interference canceller may operate/support theFD mode on the same resource. The FDR device that does not include theself-interference canceller cannot operate in the FD mode on the sameresource but may support the FD mode so as to perform informationexchange with the FDR device operating in the FD mode on the sameresource. That is, the FDR device that does not include theself-interference canceller is capable of supporting the FD mode. Thatis, even the FDR device that does not include the self-interferencecanceller may perform IDI measurement and reporting. In FIG. 11, the eNBcorresponds to an FDR device including the self-interference cancellerand UE1 and UE2 correspond to FDR devices that do not include theself-interference canceller.

In the present invention, grouping refers to grouping a plurality of UEsbased on a specific criterion.

The present invention is based on a method of configuring a group by aneNB based on IDI Information that a UE reports. If the eNB is an entityfor configuring the group, this method may be referred to as eNB centricgrouping.

Hereinafter, a situation in which the eNB performs an FD mode operationon the same resource will be described as a representative example.However, the present invention is applicable to a situation in which theUE performs the FD mode operation on the same resource and a situationin which the UE performs the FD mode operation on the same resource whenthere is no relaying by the eNB as in Device-To-Device communication(D2D). A description thereof will be given after the situation in whichthe eNB performs the FD mode operation on the same resource isdescribed. The above situations may be simultaneously generated in acell and may be simultaneously applied although they are separatelydescribed for ease of description in the present invention.

1. First Embodiment

The first embodiment of the present invention relates to a method ofinitially configuring a group sharing the same resource in a situationin which an FD operation can be performed on the same resource.

FIG. 13 is a flowchart illustrating an initial grouping configurationmethod according to a first embodiment of the present invention.

Initial grouping indicates grouping for applying an FD mode on the sameresource in a cell for the first time.

An initial grouping procedure will now be described in brief. First, aneNB determines UEs that desire to participate in grouping (S131). Inthis case, the eNB may select candidate UEs in consideration ofcapability to manage the FD mode on the same resource. If the candidateUEs are selected, the eNB transmits information or an instructionnecessary for grouping to the candidate UEs (S132). The candidate UEsmeasure IDI (S133) and report information about IDI to the eNB (S134).The eNB groups UEs based on the reported information (S135) andtransmits information about a grouping result to the corresponding UEs(S136).

Hereinafter, each step of FIG. 13 will be described in detail.

1.1 Determination of Candidate UEs

In step S131, the eNB monitors candidate UEs that are to be configuredas a group.

As a first method of determining the candidate UEs, the eNB may requestthat all UEs connected to the eNB transmit information as to whether theUEs participate in grouping. For example, the information about requestmay be transmitted through a DCI format of a PDCCH or an E-PDCCH orthrough a PDSCH. In response to the request, the UEs may transmit aresponse indicating whether to participate in grouping. For example, theresponse may be transmitted through an Uplink Control Information (UCI)format of a PUCCH or a PUSCH.

As a second method, each UE may transmit participation requestinformation. That is, the UE may transmit the information indicatingrequest for participating in the FD mode on the same resource inconsideration of characteristics of data that the UE is to transmit.Such information may be transmitted to the eNB through the UCI format ofthe PUCCH or the PUSCH.

A third method relates to the case in which the eNB is pre-aware ofinformation about a UE, for example, the case in which the eNB is awareof characteristics of data that the UE is to transmit or of a preferredUE for FD participation on the same resource. For example, the thirdmethod may correspond to the case in which a UE is ready to participatein grouping but does not currently participate in the FD mode on thesame resource. In this case, the eNB may transmit information indicatingwhether a UE is to participate in grouping to the corresponding UE. Suchinformation may be transmitted through the DCI format of the PDCCH orthe E-PDCCH or through the PDSCH.

In this case, the information indicating whether a UE is to participatein grouping may include information about an indication as to whetherthe UE is an FDR device (including a self-interference canceller)capable of operating in the FD mode on the same resource, informationabout an indication as to whether the UE is an FDR devices supportingthe FD mode on the same resource although the UE cannot operate in theFD mode on the same resource, and information about an indication as towhether the UE is an FDR device and is to request participation ingrouping. As described above, an FDR device may include aself-interference canceller and the FDR device including theself-interference canceller may operate/support the FD mode on the sameresource. An FDR device that does not include the self-interferencecanceller cannot operate in the FD mode on the same resource but cansupport the FD mode so as to perform information exchange with the FDRdevice operating in the FD mode on the same resource. That is, even theFDR device that does not include the self-interference canceller may asupport operation such as IDI measurement and reporting.

Such three types of information may be allocated through the UCI format.For example, a total of three bits is allocated through the UCI formatto the above three indications, one bit per indication. Each bitindicates “1” for acknowledgement and “0” for negative acknowledgementor vice versa.

FIG. 14 illustrates exemplary allocation of a bit indicating whether toparticipate in grouping.

For example, ‘011’ indicates that a UE cannot operate in the FD mode onthe same resource but supports the FD mode on the same resource andcurrently desires to participate in grouping, as in the UEs of FIG. 11.‘000’ may be allocated to a UE that does not participate in grouping soas to support operation in a legacy system.

An FDR device may change a grouping participation request bit inconsideration of a transmission data characteristic, a remaining powerprofile, a buffer state, etc. In addition, in order to reduce time todetermine a bit allocated to a UE by an eNB, the grouping participationrequest bit may be set so as not to perform an FD mode operation and FDmode support.

A Bit for FD mode operation and support may be desirably transmittedonly when a UE participates in grouping for the first time orparticipates in grouping again after the UE is excluded from a groupafter group configuration. If group configuration is ended, the eNB maymanage the bit together with corresponding UE_ID by setting a UE capableof performing only FD mode support to ‘0’ and a UE capable of performingan FD mode operation to ‘1’.

A UE capable of performing the FD mode operation may additionallyallocate a bit indicating an operation method in the FD mode through theUCI format. For example, the operation method may be indicated such thatif the bit is ‘0’, this indicates FD mode support and, if the bit is‘1’, this indicates the FD mode operation. The eNB may determine the bitfor the case in which the UE operates in the FD mode so as to be usedfor resource allocation.

1.2 Information Transmission for Grouping

Next, in step S132, the eNB transmits information for grouping tocandidate UEs selected based on S131.

An example of information for grouping may include an indication as towhether a corresponding UE has been selected as a candidate UE, afrequency to be identically used, and the total number N of groupingcandidate UEs. The eNB may transmit the information for grouping byallocating a bit through the DCI format of the PDCCH or through thePDSCH.

The eNB may limit operation UEs due to the number of available UEs. Inaddition, the eNB may inform a UE that has indicated that the UE canparticipate in grouping in step S131 of whether the UE has been selectedas a grouping candidate UE. In this case, a UE that has not beenselected as a candidate UE by the eNB desirably operates in a fallbackmode. The fallback mode indicates operation in half duplex as in alegacy scheme or in the FD mode on different frequencies.

1.3 IDI Measurement

Next, in step S133, a grouping candidate UE measures IDI caused by (N−1)neighbor UEs except IDI caused thereby. Measurement of IDI caused by theneighbor UEs may be performed as follows.

IDI is generated by use of the same resource. One UE may transmit anuplink UL signal and the other (N−1) UEs may receive a downlink signalin each subframe during a total of N subframes, thereby measuringReference Signal Received Power (RSRP) or Reference Signal ReceivedQuality (RSRQ) of IDI.

The magnitude of IDI with respect to each target UE may be defined as afunction having parameters of the distance between a measurement UE andthe target UE, transmission power of the target UE, and transmissiondirection of the target UE.

Meanwhile, all of N UEs included in grouping candidates may bemeasurement subject UEs. In this case, a signature for distinguishingbetween the UEs may be used.

1.4 IDI Information Reporting

Next, in step S134, N UEs may transmit UE_IDs or indexes and informationabout the measured IDI to the eNB. The information about the measuredIDI may be transmitted using the following methods.

A first method is to transmit approximate IDI Information. Each UE mayarrange IDI values measured with respect to neighboring UEs in ascendingorder or descending order and transmit an arranged order (index value)and UE_IDs of the corresponding neighbor UEs to the eNB through the UCIformat of the PUCCH or the PUSCH. According to the first method,transmission amount can be reduced by transmitting the arranged order ascompared with a method of transmitting detailed information.

A second method is to transmit detailed information. Each UE maytransmit UE_IDs of the neighboring UEs and quantized information aboutthe measured IDI values corresponding to the UE_IDs to the eNB throughthe UCI format of the PUCCH or the PUSCH.

A third method may use a hybrid form of the first and second methods atthe request of the eNB. For example, each UE may transmit the arrangedorder and UE_ID as in the first method and simultaneously transmit thequantized information for partial UE_IDs as in the second method. Inaddition, for all UE_IDs, the information of the second method may betransmitted in a long-term period and the information of the firstmethod may be transmitted in a short-term period.

In step S134, not only the information about IDI but also additionalinformation to be considered for grouping may be transmitted.

For example, quantized information about IDI processing capabilities ofa UE may be transmitted (through the UCI format of the PUCCH or thePUSCH). Alternatively, the best frequency band based on a CSI channelfed back by the UE, a remaining power profile of the UE, etc. may betransmitted (through the UCI format of the PUCCH or the PUSCH).

1.5 Grouping Implementation

Next, in step S135, the eNB performs grouping based on the informationreceived in step S134 and sets a group ID of each UE.

Grouping may be performed based on the magnitude of IDI or an orderarranged by the magnitude of IDI. Upon additionally receivinginformation other than the IDI measurement values, the eNB may performgrouping using the additional information.

The eNB may configure a group considering a specific threshold of IDI ofeach UE or the size of each preconfigured group. In this case, thethreshold may be determined according to capabilities of an IDImitigation or cancellation algorithm.

The size of each group (the number of UEs included in each group) may bepredetermined in consideration of available resources. Alternatively,the size of a group may be set by configuring the group only when an IDIvalue is equal to or greater/less than a specific threshold. A minimumsize of a group is 1 and this indicates that an IDI value significantlydeviates from the threshold and that a specific resource is allocatedonly to the corresponding UE. That is, this case corresponds to afallback mode operation.

As a first method of IDI based grouping by the eNB, a group of UEsgenerating much IDI may be configured. For example, a group of UEshaving IDI values equal to or greater than the specific threshold may beconfigured. Such grouping may be defined as worst relation basedgrouping. That is, UEs having significant IDI are configured as onegroup.

As a second method of IDI based grouping by the eNB, a group of UEsgenerating less IDI may be configured. For example, a group of UEshaving IDI values equal to or less than the specific threshold may beconfigured. Such grouping may be defined as best relation basedgrouping. That is, UEs having less IDI may be configured as one group.

According to a group configured by the above two methods, resourceallocation in the group may be performed as follows.

In a worst relation based group, since IDI values of UEs in the groupare greater than the threshold, an IDI avoidance technique (e.g., abeamforming technique) may be used when the UEs in the group use thesame resource. In addition, interference may be avoided by multiplexingthe UEs in the group based on FDM and UEs between groups may beconfigured to operate in/support an FD mode on the same resource.Operation/support of the FD mode on the same resource by UEs betweengroups favorably uses a Successive Cancellation (SC) method which is aninterference cancellation technique. This is because the SC method showsbetter cancellation performance as the difference in signal strength ofinterference is big.

In a best relation based group, UEs in a group are configured to operatein/support the FD mode on the same resource and UEs between groups maybe multiplexed based on FDM, thereby avoiding interference.

The FD mode may be performed on the same resource between the worstrelation based group and the best relation based group. In this case,the SC method as an interference cancellation technique is favorablyapplied. As described above, the SC method exhibits better performanceas the difference in signal strength of interference is big. Forexample, if a first UE, a second UE included in the worst relation basedgroup with respect to the first UE, and a third UE included in a bestrelation based group with respect to the first UE are selected by theeNB and the three UEs support the FD mode on the same resource, the SCmethod may be sequentially applied to the second UE in the worstrelation based group and the third UE in the best relation based group.Then, performance increases relative to the case in which only UEs inthe same relation group are selected.

1.5.1 Example of Worst Relation Based Grouping

FIG. 15 (a) illustrates exemplary arrangement of an eNB and 8 UEs forcell-specific grouping and FIG. 15(b) illustrates exemplary groupconfiguration when worst relation based grouping is ended. In this case,it is assumed that IDI is proportional to the distance between UEs.

FIG. 16 illustrates arrangement based on IDI measured by the UEs of FIG.15(a) in order of a high value. In FIG. 16, the first column indicatesUEs that desire to measure IDI and the first row indicates target UEs,IDI of which is to be measured.

For example, the second row of FIG. 16 indicates that measured IDI has ahigh value in order of d, g, b, e, f, h, and c when UE a measures IDI ofthe other UEs. This method corresponds to the first method of the IDIinformation reporting method of section 1.4. Specifically, a low indexis used for a high IDI value. Hereinafter, grouping will be performedbased on the assumption that a high IDI value has a low index. However,grouping may be performed based on the assumption that a high IDI valuehas a high index value.

When a measurement UE is identical to a target UE, since IDI is notmeasured and this is meaningless, IDI is indicated by ‘0’.

Averages of values in the columns of FIG. 16 are shown in FIG. 17. Anaverage of the values in each column may relatively indicate how much ameasurement UE is separated from the center of all UEs.

Hereinafter, a detailed procedure will be described of grouping UEs asillustrated in FIG. 15(b) by performing worst relation based groupingbased on the measurement values of FIG. 16 in arrangement of the eNB andthe UEs of FIG. 15(a).

FIG. 18 illustrates selection of UEs for configuring a first group.

Since a low number (low index) in a table indicates that a target UE hasa great effect (of IDI) on a measurement UE, an eNB selects target UEshaving a great effect on each measurement UE. In an example of FIG. 18,three values having a great effect on each measurement UE (three lowvalues) in each column are selected. In this case, the three values arearbitrarily selected and the number of selected values may differaccording to the total number of groups. In addition, when index valuesare equal, all of the same index values are selected. However, thepresent invention is not limited thereto.

For example, in the first column of FIG. 18, ‘2’ corresponding to thelowest value is selected. When expressing ‘2’ as (row-column), two ‘2’sin (d-a) and (g-a) are selected. Since it has been determined that thethree values having a great effect are selected, the next value ‘7’ isselected and all of the same values are selected. As a result, allvalues are selected in the first column.

The second column of FIG. 18 will now be described. The lowest value inthe second column is ‘1’ and one ‘1’ in (e-b) is selected. The nextlowest value is ‘3’ and ‘3’s in (a-b), (d-b), (g-b), and (h-b) areselected.

Referring to the third column of FIG. 18, the lowest value in the thirdcolumn is ‘1’, two ‘1’s in (f-c) and (h-c) are selected. The next lowestvalue is ‘4’ and one ‘4’ in (e-c) is selected. Consequently, threevalues are selected in total.

In this way, low values in the other columns are selected and theselected values are shaded in the table of FIG. 18.

Next, an average of values in each row with respect to a selected targetUE is calculated. The rightmost column of FIG. 18 indicates acorresponding average. A low average may mean that there is a smallnumber of target UEs having an effect on a measurement UE, because threetarget UEs having low values have been selected. In addition, a lowaverage may also mean that a measurement UE is biased toward one side.In the example of FIG. 15(a), it may be appreciated that averages of UEsa, d, and g biased toward one side are low. On the contrary, a highaverage may mean that a UE is greatly affected by many UEs.

Accordingly, if the size of the first group is determined as 3, UEs a,d, and g having the three lowest averages are set as the first group.

FIG. 19 illustrates selection of target UEs as in FIG. 18 with respectto the other UEs except for UEs a, d, and g configured as a group.

For example, the lowest value ‘1’ in the first column is selected andthe next lowest value ‘3’ is selected. In the third column for example,the lowest value ‘1’ is selected and the next lowest value ‘3’ isselected. The same values are all selected. In this way, values in eachcolumn are selected.

Next, as in FIG. 18, an average of values of each row is calculated withrespect to a selected target UE. The rightmost column of FIG. 19indicates a corresponding average. A low average means that there is asmall number of UEs having an effect on a measurement UE. Therefore,when the size of a second group is 2, UEs b and e having the two lowestaverage values are configured as the second group.

Grouping may be performed by repeating the above method with respect tothe other UEs. In the embodiment of FIG. 15, a total of three groups isexemplarily configured.

As described above, worst relation based grouping has been described insection 1.5.1 based on the assumption that a high IDI value has a lowindex. However, worst relation based grouping may be performed based onthe assumption that a high IDI value has a high index. In this case, inFIG. 16, a predetermined number of high indexes may be selected and theabove method may be identically applied based on a high average value ofeach row.

1.5.2 Example of Best Relation Based Grouping

FIG. 20 illustrates configuration of a first best relation based groupwhen IDI is arranged in order of a low value contrary to FIG. 16. Thatis, ‘1’ in FIG. 16 becomes ‘7’, ‘2’ in FIG. 16 becomes ‘6’, and ‘7’ inFIG. 16 becomes ‘1’. This method corresponds to the first method in theIDI information reporting method of section 1.4 and, specifically, a lowIDI value is set to have a low index. Hereinafter, grouping will beperformed based on the assumption that a low IDI value has a low index.However, grouping may be performed based on the assumption that a lowIDI value has a high index.

A low value in a table indicates that a target UE has a less effect on ameasurement UE.

First, a target UE having less effect on a measurement UE (having a lowvalue) is selected. In the example of FIG. 20, the size of each group isset to 2 and two low values are selected in each column. The size of agroup and selected values, set to 2, are arbitrarily determined and mayvary with the total number of groups. In addition, while all of the samevalues are selected when the same values are present, the presentinvention is not limited thereto. Since the highest IDI value shouldsatisfy a value equal to or less than a threshold value in best relationbased grouping, target UEs may be not selected according to thethreshold value. If the target UEs are not selected, differentfrequencies/times may be allocated to the UEs. Hereinafter, the case inwhich an IDI measurement value is equal or less than the threshold valuewill be described as an embodiment.

Since a low value is assigned based on a low IDI value and two lowvalues are selected, a large number of UEs selected in each columnindicates that a target UE is separated from measurement UEs by a longdistance. For example, a target UE a has 5 selection values and it maybe appreciated in FIG. 15(a) that the target UE a is located at an endside.

For best relation based grouping, UEs which are small in number selectedin each column and have a greatest effect on IDI are selected so as toreduce the number of UEs having a greatest effect on IDI. For example,UEs having a small number of selected values in respective columns are band h and the number of selected values in each column is 2. A UE havinga greatest effect on IDI indicates that the UE has a large value. Avalue selected in a column of the UE b is 4, which is greater than 2selected in a column of the UE h. Therefore, the UE b is selected. Thatis, in FIG. 20, a measurement UE c or f may be configured as a groupwith respect to the target UE b.

FIG. 21 illustrates selection of target UEs as in FIG. 20 except for UEsb and c to configure a second group after the UEs b and c are configuredas a group.

When the same method as first grouping is used, among UEs d, g, and hhaving a lower number of values selected in each column, the UE d havingthe greatest value 3 is selected. In a column of the UE d, a UE f has alarge value as 3. Therefore, the UEs d and f are configured as onegroup.

Similarly, FIG. 22(a) and FIG. 22(b) illustrate selection of target UEsfor configuring a third group and a fourth group, respectively. Then,UEs g and e are configured as a group in FIG. 22(a) and UEs a and h areconfigured as a group in FIG. 22(b).

That is, best relation based grouping in FIG. 15(a) may be configured asin FIG. 23. That is, each of UEs b and c, UEs d and f, UEs g and e, andUEs a and h may be configured as a group.

As described above, best relation based grouping has been described insection 1.5.2 based on the assumption that a low IDI value has a lowindex. However, best relation based grouping may be performed based onthe assumption that a low IDI value has a high index. In this case, inFIG. 20, a predetermined number of high indexes may be selected and theabove method may be identically applied.

In addition, instead of using an index value, grouping may be directlyperformed using a quantized IDI measurement value. That is, an eNB mayperform grouping of UEs satisfying a threshold value directly using anIDI value. For example, in worst relation based grouping, UEs having IDIvalues equal to or greater than a specific threshold value areconfigured as one group and, in best relation based grouping, UEs havingIDI values equal to or less than the specific threshold value may beconfigured as one group. In this case, the size of each group shouldsatisfy a preset group size and a threshold value. For example, if thesize of any group is preset to 3 and there are only two UEs satisfyingthe threshold value, the size of this group should be 2.

1.6 Transmission of Grouping Result Information

In step S136, the eNB may transmit information about a configured groupto UEs.

Specifically, the information about the configured group may betransmitted as follows according to the amount of downlink transmission.

As a first method, the eNB may transmit only group IDs to which UEsbelong to all of the UEs. For example, information about the group IDsmay be transmitted by allocating a bit through a DCI format of a PDCCHor through a PDSCH. Using the information, each UE may measure IDI forUEs other than UEs in a group to which the UE belongs.

As a second method, the eNB may transmit a group ID to which a UEbelongs and neighbor group IDs to all UEs. For example, a group ID towhich the UE belongs and neighbor group IDs may be transmitted throughthe PDCCH or the PDSCH. The eNB selects group IDs satisfying IDI valuesequal to or greater/less than a specific threshold value as neighborgroup IDs using the reported IDI information and then transmits theneighbor group IDs. Next, each UE in a group ID may measure IDI onlywith respect to UEs belonging to the received neighbor group IDs,thereby reducing overhead for IDI measurement.

As a third method, the eNB may transmit all group IDs and UE_IDsbelonging to corresponding groups to all UEs. For example, thisinformation may be transmitted through the PDCCH or the PDSCH. Asopposed to the second method, each UE measures IDI for one UE per groupID during IDI measurement and measures IDI only with respect to UEsbelonging to a group satisfying an IDI value equal to or greater/lessthan a specific threshold value, thereby reducing overhead for IDImeasurement.

Meanwhile, information transmitted to a UE may includemeasurement/reporting period information and this information may betransmitted through higher layer signaling such as RRC.

2. Second Embodiment

The second embodiment of the present invention relates to a method forupdating grouping after initial grouping of the first embodiment isperformed.

Grouping update indicates maintenance or update of group configurationdue to IDI re-measurement or reporting in a situation in which a groupis configured and operates in an FD mode on the same resource. Aconfigured group may be changed due to participation of a new candidateUE in a group or dropping of a previous candidate UE from a group.

FIG. 24 is a flowchart illustrating grouping update according to asecond embodiment of the present invention.

First, a grouping update procedure will now be described in brief. AneNB determines whether there is a candidate UE that desires toparticipate in grouping or a UE that desires to stop participating in anFD mode on the same resource (S2401). If a new candidate UE is present,the eNB informs all groups that the corresponding candidate UE is atarget UE for IDI measurement and, if a UE that desires to stopparticipating in the FD mode is present, the eNB informs groupsperforming measurement of the corresponding UE that the UE desires tostop participating in a group (S2403). If there is no UE to be changed,a UE determination period, an IDI measurement period, or an IDIreporting period may be changed (S2404). IDI measurement by a UE may beperformed according to a set period (S2406) or according to aninstruction by the eNB (S2407). A UE measuring IDI may report IDIinformation to the eNB according to a set period (S2409) or according toan instruction by the eNB (S2410). The eNB updates group information ofUEs based on the reported information (S2411) and transmits the updatedgroup information to the corresponding UEs (S2412).

Hereinafter, each step of FIG. 24 will be described in detail.

2.1 Determination of Grouping Candidate UE

In step S2401, the eNB determines whether there is a new candidate UEthat desires to participate in grouping or a UE that desires to stopparticipating in an FD mode on the same resource.

The UE that desires to stop participating in the FD mode operates in afallback mode.

2.1.1 Method of Determining Grouping Candidate UE

The eNB may check whether there is a UE that desires to participate inthe FD mode on the same resource using the following methods.

As a first method, an FDR device may allocate one bit indicating whethera corresponding UE has been included in a group through a UCI format ofa PUCCH or a PUSCH. The eNB determines whether a UE is a groupingparticipation/dropping candidate UE using both this bit and the bit fora grouping participation request in FIG. 14. For example, if thegrouping participation request bit is ‘1’ and the bit indicating that acorresponding UE has been included in a group is ‘0’, the UE correspondsto a new candidate UE that is to participate in grouping.

FIG. 25 illustrates an example of determining a grouping candidate UEusing a bit for a grouping participation request and a bit indicatingwhether the UE has been included in a group.

As a second method, the eNB determines a grouping participation/droppingcandidate UE using the bit for the grouping participation request inFIG. 14. If the eNB stores a group ID of a configured group and UE_IDsof UEs included in the group, the group ID and UE_IDs may be usedinstead of the bit indicating whether a corresponding UE has beenincluded in a group. For example, if the grouping participation requestbit is ‘1’ and a UE_ID of a corresponding UE is not present in thestored UE_IDs, the eNB may determine that the UE is a new UE that is toparticipate in grouping.

As a third method, a UE transmits the grouping participation request bitin consideration of a state included in a group (e.g., reception of acorresponding group ID). In this case, the grouping participationrequest bit may be used instead of the bit allocated to indicate whethera corresponding UE has been included in a group. In this case, if thegrouping participation bit is ‘0’, the eNB may determine that the UE isto stop participating in the FD mode and, if the grouping participationbit is ‘1’, the eNB may determine that the UE is a new UE that is toparticipate in grouping.

2.1.2 Grouping Candidate Determination Timing

The eNB may periodically perform grouping update. Specifically, groupingupdate may be performed with respect to UEs participating in an FD modethrough steps S2403 and S2405. The determination timing and operation ofgrouping candidate UEs may be performed as follows.

As a first method, the eNB determines grouping candidate UEs whenevergrouping update is performed.

As a second method, the eNB periodically determines grouping candidateUEs at a candidate UE determination period. The candidate UEdetermination period may be fixed or may be changed to be long in anenvironment in which a group is not frequently changed. In this case,when a group is changed or a grouping candidate UE is determined, theincreased period may be reset to a first set period.

Specifically, the candidate UE determination period may be determined asfollows relative to the grouping update period. As a first method, thecandidate UE determination period may be shorter than the groupingupdate period. This method may be used when the eNB predetermines an FDmode participation stopping UE with respect to partial groups at everycandidate UE determination period. As a second method, the candidate UEdetermination period may be longer than the grouping update period. Inthis case, overhead for determining candidate UEs can be reduced. Ifgrouping update is performed at a period at which the candidate UEs arenot determined, it may be determined that grouping target UEs are notchanged in step S2402.

As a third method, the eNB may determine the grouping candidate UEs as aresponse to occurrence of a UE request. For example, a UE may requestnew participation in grouping through UE power-on or activation of anFDR device of a user. Alternatively, a UE may request dropping the FDmode by UE power-off, inactivation of an FDR device of a user, or aremaining power profile less than a reference value. The candidate UEdetermination period may be determined as an immediate period or aconstant set period. Alternatively, when a UE moves between groups, theUE may request a grouping update.

Further, the candidate UE determination period may increase bysimultaneously using the second method and the third method. In thiscase, overhead for determining the candidate UEs can be reduced.

2.1.3 Determination of Grouping Candidate UE During Movement of UEBetween Groups

Grouping update may be requested not only in the case in which a newcandidate UE that is to participate in grouping or a UE that desires tostop participating in the FD mode on the same resource is present butalso in the case in which UEs that have already been configured as agroup move between groups. Operation when a UE moves between groups maybe as follows.

As a first method, grouping update is performed with respect to all UEsat every grouping update or at a constant period.

As a second method, if the state of a UE is changed by a predeterminedcriterion or more, for example, if a UE moves at a high speed, the UEmay operate in a fallback mode. This corresponds to FD modeparticipation stop of the FD and the UE drops from a grouping updateprocedure and operate as a new candidate UE that is to participate ingrouping at a next grouping update timing.

As a third method, a new candidate UE that is to participate in groupingmay directly transmit a request. For example, the UE may transmit therequest by setting the bit for the grouping participation request to ‘1’and setting the bit indicating whether a corresponding UE has beenincluded in a group to ‘0’. Upon receiving the request, the eNBdetermines whether a corresponding UE_ID is present in an IDImeasurement target list or whether a set group ID is present. When thereis a set group ID but ‘0’ is received as the bit indicating whether theUE has been included in a group, the eNB may perform grouping update.

2.1.4 Method of Allocating IDI Measurement Frequency to GroupingCandidate UE

In step S2401, the eNB may allocate a frequency for IDI measurement togrouping candidate UEs as illustrated in FIG. 26.

FIG. 26 (a) illustrates exemplary allocation of a common frequency fcofor IDI measurement to all UEs. In this case, all UEs use time for Nsubframes used when N UEs measure IDI as in step S1303.

FIG. 26 (b) illustrates exemplary allocation of different IDImeasurement frequencies in a first time domain and a second time domain.

In the second time domain, if both the bit for the groupingparticipation request and the bit indicating whether a UE has beenincluded in a group are ‘1’, exclusive frequencies f1, f2, and f3 areallocated to respective groups during a partial time. UEs in each groupcommonly use a frequency allocated to the group.

In the first time domain, if the bit for the grouping participationrequest is ‘1’ and the bit indicating whether a UE has been included ina group is ‘0’, that is, if there is a UE that is to newly participatein grouping, the eNB allocates a common frequency fco for measuring theIDI of the UE to all UEs.

For example, if the number of UEs included in each of three groups is Aand the number of UEs that are to newly participate in grouping is B,exclusive frequencies are allocated during A subframes and a commonfrequency is allocated during B subframes. In this case, B UEs transmituplink signals during B subframes and the other (3*A+(B−1)) UEs receivedownlink signals during the same time, thereby performing IDImeasurement.

In the method of FIG. 26(a), a total of (3*A+B) subframes is consumedfor IDI measurement and, in the method of FIG. 26(b), a total of (A+B)subframes is consumed.

In the method of FIG. 26(b), since a UE which has a probability of beingreconfigured as another group by moving into another group may notcorrectly consider a channel environment, the above two methods may besimultaneously performed with different periods. Hereinafter, forconvenience of description, movement of a UE between groups will beincluded in change of a grouping candidate target UE.

2.2 Change of Grouping Target UE

In steps S2402 and S2403, the eNB may transmit information about a UE tobe changed using the following methods after determining the groupingcandidate target UE in step S2401.

By newly allocating UE_ID to a UE that is to newly participate ingrouping, the eNB may inform grouping update target UEs (another new UEthat desires to participate in grouping and all UEs in a current groupexcept for a UE that is to stop participating in an FD mode) of thecorresponding UE_ID or an IDI measurement target list in which thecorresponding UE_ID is included. Such information may be transmittedthrough a PDCCH or a PDSCH. The IDI measurement target list may includeUE_IDs of the grouping update target UEs or UE_IDs of UEs belonging topartial groups.

In consideration of scheduling or available resources, the eNB maytransmit the UE_ID or the IDI measurement target list to all UEs in acurrent group except for a UE that is to stop participating in the FDmode or to a group to which a changed UE belongs. Such information maybe transmitted through the PDCCH or the PDSCH.

If there are no UEs to be changed in step S2402, the eNB may transmitthe IDI measurement target list through the PDCCH or the PDSCH.Alternatively, the eNB may allocate and transmit a bit indicating that aprevious IDI measurement target list should be reused through the PDCCHor the PDSCH.

When UE has not received UE_ID, the IDI measurement target list, or theprevious list reuse indicator (referred to as IDI measurement targetlist for ease of description), the UE may reuse the previous list. Inthis case, even when the UE has not received a UE_ID of an FD modeparticipation stopping UE, since there is no UE_ID during IDImeasurement, an IDI measurement value is not present. If a UE that hasnot received the list has not received a UE_ID of a UE that is toparticipate in grouping, the UE may determine that there is IDIexceeding a total size of IDI and inform the eNB of the determinedresult. Alternatively, if a UE has not received the IDI measurementtarget list, the UE may request that the eNB retransmit the IDImeasurement target list.

In step S2404, if there are no UEs to be changed with respect to a UEdetermination period, an IDI measurement period, or an IDI reportingperiod, which are determined by the eNB, or if there are no UEs to bechanged within a predetermined time, a corresponding period may beincreased. In this case, the eNB may increase the period by checking thecase in which group configuration is not additionally changed, an IDIarrangement order in a group is not changed, or a variation occurs inIDI size less than a specific value in a group.

2.3 Interference Measurement

In steps S2405 and S2407, the eNB may instruct grouping update targetUEs to perform IDI measurement. Then, the UEs may immediately measureIDI. Alternatively, the eNB may instruct partial groups including FDmode participation stopping UEs to perform IDI measurement. Even whenthere is a measurement period as in step S2406, the eNB may instruct aUE to perform IDI measurement. For example, if the measurement period islong and a grouping target UE is not frequently changed, when thegrouping target UE is changed, the eNB may instruct the UE to measureIDI.

In step S2406, the UE may periodically measure IDI using ameasurement/reporting period included in information transmitted by theeNB to the UE in step S1306 or S2412 or using a period set as a systemparameter. Periodic IDI measurement by the UE may be performed using thefollowing methods.

As a first method, an X time or a Transmit Time Interval (TTI) period isset as a system parameter and IDI for all UEs is measured.

As a second method, a Y time or TTI period different from the X time orTTI is set as the system parameter and IDI only for partial groups inwhich an FD mode participation stopping UE is included is measured.According to how many grouping target UEs are changed, the case in whichY>X may occur.

The above two methods may be simultaneously used and, in this case,overhead for IDI measurement can be reduced.

The UE measures IDI using a frequency allocated for IDI measurement instep S2401.

Meanwhile, in steps S2406 and S2407, the UE may deny IDI measurementbased on a remaining power profile.

2.4 Interference Information Reporting

Next, in steps S2408 and S2410, the eNB may instruct grouping updatetarget UEs to report measured IDI information. Then, the UEs mayimmediately report the measured IDI information. The UEs may performmeasurement IDI information reporting only for a group in which an IDIarrangement order is changed or a variation in IDI size equal to orgreater than a specific value occurs. Even when a period is present asin step S2409, if the eNB instructs the UE to perform IDI measurementonly for partial groups including FD mode participation stopping UEs,the eNB may instruct the UEs of the corresponding groups to report IDIinformation.

In step S2409, the UE may periodically report UE indexes and IDIInformation in the form of step S134 using a measurement/reportingperiod included in the information transmitted by the eNB to the UE insteps S136 and S2412 or using a period set as a system parameter.Periodic interference information reporting by the UE may be performedas follows.

As a first method, an X time or a TTI period is set as a systemparameter and IDI measured for all UEs and UE indexes may be reported.

As a second method, a Y time or a TTI period different from the X timeor TTI is set as the system parameter and IDI measured only for partialgroups in which FD mode participation stopping UEs are included and UEindexes may be reported. According to how many grouping target UEs arechanged, the case in which Y>X may occur.

The above two methods may be simultaneously used and, in this case,overhead for IDI information reporting can be reduced.

If an IDI arrangement order is not changed or a variation in IDI sizeequal to or less than a specific value occurs, reporting may not beperformed in steps S2409 and S2410 and, instead, an indicator indicatingthat reference is made to previous reporting may be transmitted to theeNB through the PUCCH or the PUSCH. In this case, steps S2411 and S2412may be omitted. As in step S134, not only information about IDI but alsoinformation not based on an IDI measurement value, which may beconsidered for grouping, may be further transmitted to the eNB.

When the eNB has not received reporting from the UE for a predeterminedtime, the eNB may perform steps S2411 and S2412 by referring to previousreporting by default. Alternatively, steps S2411 and S2412 may beomitted.

As described above, in steps S2406 and S2407, the UE may deny IDImeasurement due to a remaining power profile, etc. That is, the UE maynot perform transmission of a distinction signal between UEs and ahearing attempt. In this case, a bit indicating that IDI measurement hasbeen denied may be transmitted in steps S2409 and S2410 through thePUCCH or the PUSCH. Alternatively, the UE may not perform any reportingand the eNB may check a UE having a remarkably decreased IDI value whilewaiting for reporting. Through this, the eNB may be aware that thechecked UE is the UE that has denied IDI measurement.

2.5 Grouping Information Update

In step S2411, grouping may be performed using the same method as inS135. In addition, the eNB may store a previous group ID allocated foreach UE. Thus, the eNB may check UEs having frequently changed group IDsand may perform the following operations.

First, when multiple group IDs are allocated to one UE, the eNB mayrecognize that the UE is located at a boundary between groups. The IDIvalue measured by this UE may be used as a threshold referenced forgrouping.

Second, if a group ID which is not repeated within a predetermined timewith respect to any one UE is allocated, the eNB may be aware that theUE moves. Since IDI measurement/reporting and grouping should always beperformed with respect to such a UE, the eNB may remove the UE from theFD mode on the same resource through fallback.

Step S2412 may be performed identically to step S136. If a result ofperforming grouping in step S2411 is not changed, a signal indicatingthat grouping information transmitted previously to UEs should bemaintained may be transmitted to UEs belonging to a group having anunchanged grouping result. This information may be indicated byallocating one bit through the DCI format of a PDCCH or through a PDSCH.

If there is no grouping participation request any more in step S2413,the eNB ends grouping update.

The present invention is applicable even to a situation in which a UEperforms an FD mode operation on the same resource.

FIG. 27 illustrates an exemplary FD mode operation performed by a UE onthe same resource.

As in FIG. 27(a), since a UE may receive IDI from an eNB, the presentinvention may be applied by regarding the eNB as the UE in the abovedescription. In this case, an IDI reporting procedure and groupingresult information transmission within the eNB are not performed.

The present invention is applicable to a situation in which a UEperforms an FD mode operation on the same resource when there is no datarelaying by an eNB as in D2D communication of FIG. 27(b). While datatransmission through the eNB is not performed in D2D communication, theUE performs feedback to the eNB for scheduling management by the eNB.Therefore, the procedure of the present invention may be identicallyperformed.

FIG. 28 illustrates a BS and a UE that are applicable to an embodimentof the present invention.

If a wireless communication system includes a relay, communication on abackhaul link is performed between the BS and the relay andcommunication on an access link is performed between the relay and theUE. Accordingly, the BS or the UE shown in FIG. 20 may be replaced withthe relay according to situation.

Referring to FIG. 28, a wireless communication system includes a BS 2810and a UE 2820. The BS 2810 includes a processor 2813, a memory 2814, andRadio Frequency (RF) units 2811 and 2812. The processor 2813 may beconfigured to perform the procedures and/or methods proposed in thepresent invention. The memory 2814 is connected to the processor 2813and stores various types of information related to operations of theprocessor 2813. The RF units 2811 and 2812 are connected to theprocessor 2813 and transmit and/or receive radio signals. The UE 2820includes a processor 2823, a memory 2824, and RF units 2821 and 2822.The processor 2823 may be configured to perform the proposed proceduresand/or methods according to the present invention. The memory 2824 isconnected to the processor 2823 and stores various types of informationrelated to operations of the processor 2823. The RF units 2812 and 2822are connected to the processor 2823 and transmit and/or receive radiosignals. The BS 2810 and/or the UE 2820 may include a single antenna ormultiple antennas.

The embodiments of the present invention described above arecombinations of elements and features of the present invention in apredetermined form. The elements or features may be considered selectiveunless otherwise mentioned. Each element or feature may be practicedwithout being combined with other elements or features. Further, anembodiment of the present invention may be constructed by combiningparts of the elements and/or features. Operation orders described inembodiments of the present invention may be rearranged. Someconstructions of any one embodiment may be included in anotherembodiment and may be replaced with corresponding constructions ofanother embodiment. It is obvious to those skilled in the art thatclaims that are not explicitly cited in each other in the appendedclaims may be presented in combination as an embodiment of the presentinvention or included as a new claim by subsequent amendment after theapplication is filed. A specific operation described as being performedby the BS in this disclosure may be performed by an upper node of the BSin some cases. That is, it is apparent that, in a network comprised of aplurality of network nodes including the BS, various operationsperformed for communication with the UE can be performed by the BS ornetwork nodes other than the BS. The term BS may be replaced with theterms fixed station, Node B, eNode B (eNB), access point, etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to exemplaryembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, an embodiment of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. Software code may be stored in a memory unit and executedby a processor. The memory unit may be located at the interior orexterior of the processor and may transmit and receive data to and fromthe processor via various known means.

The memory unit may be located inside or outside the processor toexchange data with the processor by various known means.

The detailed description of the preferred embodiments of the presentinvention has been given to enable those skilled in the art to implementand practice the invention. Although the invention has been describedwith reference to exemplary embodiments, those skilled in the art willappreciate that various modifications and variations can be made in thepresent invention without departing from the spirit or scope of theinvention described in the appended claims. Accordingly, the inventionshould not be limited to the specific embodiments described herein, butshould be accorded the broadest scope consistent with the principles andnovel features disclosed herein.

The present invention may be carried out in other specific ways thanthose set forth herein without departing from the spirit and essentialcharacteristics of the present invention. The above detailed descriptionis therefore to be construed in all aspects as illustrative and notrestrictive. The scope of the invention should be determined byreasonable interpretation of the appended claims, and all changes comingwithin the meaning and equivalency range of the appended claims are tobe embraced therein. Claims that are not explicitly cited in theappended claims may be presented in combination as an exemplaryembodiment of the present invention or included as a new claim bysubsequent amendment after the application is filed.

INDUSTRIAL APPLICABILITY

The present invention may be used in wireless communication devices suchas a UE, a relay, and an eNB.

1. A method of allocating a resource by a Base Station (BS) in awireless access system supporting Full Duplex Radio (FDR) transmission,the method comprising: selecting a candidate User Equipment (UE) to beconfigured as a group among a plurality of UEs; transmitting informationabout group configuration to the candidate UE; receiving interferenceinformation about inter-device interference from the candidate UE;configuring a plurality of UEs as at least one group based on theinterference information; and allocating a resource to the UEsconfigured as the group on a group basis.
 2. The method according toclaim 1, wherein the group is configured to include a plurality of UEshaving great interference, and wherein the allocating the resourceincludes: allocating the resource such that the UEs included in thegroup use different resources, and UEs included in different groupsoperate in a Full Duplex (FD) mode on a same resource.
 3. The methodaccording to claim 2, wherein the group is configured to include UEshaving values of the interference information equal to or greater than athreshold value to configure a worst relation based group.
 4. The methodaccording to claim 1, wherein the group is configured to include aplurality of UEs having less interference, and wherein the allocatingthe resource includes: allocating the resource such that the UEsincluded in the group operate in a Full Duplex (FD) mode on the sameresource, and UEs included in different groups use different resources.5. The method according to claim 4, wherein the group is configured toinclude UEs having values of the interference information equal to orless than a threshold value to configure a best relation based group. 6.The method according to claim 1, wherein the interference informationincludes values indexed in order of magnitude of interference valuemeasured by the candidate UE with respect to a plurality of neighborUEs.
 7. The method according to claim 1, wherein the selecting thecandidate UE includes receiving first information as to whether the UEis able to operate in a Full Duplex (FD) mode on the same resource,second information as to whether the UE supports an FD operation ofanother device although the UE is unable to operate in the FD mode onthe same resource, and third information as to whether the UE requestsparticipation in grouping.
 8. A Base Station (BS) for allocating aresource in a wireless access system supporting Full Duplex Radio (FDR)transmission, the BS comprising: a Radio Frequency (RF) unit; and aprocessor, wherein the processor is configured to select a candidateUser Equipment (UE) to be configured as a group among a plurality ofUEs, transmit information about group configuration to the candidate UE,receive interference information about inter-device interference fromthe candidate UE, configure a plurality of UEs as at least one groupbased on the interference information, and allocate a resource to theUEs configured as the group on a group basis.
 9. The BS according toclaim 8, wherein the group is configured to include a plurality of UEshaving great interference, and wherein the processor allocates theresource such that the UEs included in the group use differentresources, and UEs included in different groups operate in a Full Duplex(FD) mode on a same resource.
 10. The BS according to claim 9, whereinthe group is configured to include UEs having values of the interferenceinformation equal to or greater than a threshold value to configure aworst relation based group.
 11. The BS according to claim 8, wherein thegroup is configured to include a plurality of UEs having lessinterference, and wherein the processor allocates the resource such thatthe UEs included in the group operate in a Full Duplex (FD) mode on asame resource, and UEs included in different groups use differentresources.
 12. The BS according to claim 11, wherein the group isconfigured to include UEs having values of the interference informationequal to or less than a threshold value to configure a best relationbased group.
 13. The BS according to claim 8, wherein the interferenceinformation includes values indexed in order of magnitude ofinterference value measured by the candidate UE with respect to aplurality of neighbor UEs.
 14. The BS according to claim 8, wherein theprocessor is configured to receive first information as to whether theUE is able to operate in a Full Duplex (FD) mode on the same resource,second information as to whether the UE supports an FD operation ofanother device although the UE is unable to operate in the FD mode onthe same resource, and third information as to whether the UE requestsparticipation in grouping.